Few things tantalize U.S. workers more during the day than food, new research shows.

A study by Accounting Principals found that food is the most serious spending weakness for American workers. Sixty-five percent of workers said going out to lunch or buying snacks is their biggest spending pitfall, which far exceeds other spending such as happy hours and shopping during work.

Overall, U.S. employees are spending thousands of dollars are years on coffee and going out to lunch. Of those surveyed, 82 percent spend an average of $21 a week on coffee, with nearly 90 percent spending an average of $36 a week on lunch.

"American workers have proved resilient at getting their careers back on track, but now it's important to be cautious of how they spend their hard-earned pay," said Jodi Chavez, senior vice president of Accounting Principals. "Oftentimes, the little, unmemorable spends we may make throughout the day are the ones with the biggest impact on our wallets."

The study discovered this year's payroll tax increase has forced some employees to slightly curb their spending. Twenty percent of workers have cut back the most on going out to bars and restaurants and 19 percent are going out to lunch less frequently.

However, despite the average worker taking home $130 less per month because of the tax increase, 22 percent of those surveyed have not trimmed their spending at all.

"Although Americans are cutting back on some purchases during the week, it doesn't seem to be enough to keep them from dipping into their long-term savings," said Chavez.

The research found that nearly 30 percent of employed Americans have prematurely pulled money out of their retirement funds, such as 401(k)s or IRAs to pay for unexpected expenses such as health-care costs, home or car repairs, or needing money during periods of unemployment.

"With the majority of top companies offering ways to help their employees invest in their futures, the savviest workers are taking full advantage of these unique rewards and opportunities," Chavez said.

The study was based on surveys of 1,020 employed Americans over the age of 18.